Microwave circuits are employed for coupling electromagnetic energy between microwave components such as horns, circulators, signal generators and receivers. The conduits by which the electromagnetic energy is coupled between the microwave components may be constructed in various forms of transmission lines ranging from stripline to waveguide, and frequently include various forms of power couplers, power splitters, and power combiners. Such conduits allow microwave signals to be split among a number of microwave components, and also allow the combining of signals from a plurality of microwave components.
Of particular interest herein are complex microwave circuits employing coaxial transmission lines, particularly rigid coaxial transmission lines having a center conductor of rectangular or square cross section, for interconnecting numerous microwave components. Such circuitry is found, by way of example, in large antenna arrays employing many horn radiators coupled by signal combiners and/or splitters to produce a desired radiation pattern. In such complex microwave structures, it is frequently necessary to bring signals from various parts of the structure to other parts of the structure by coaxial lines which cross over each other. An example of such routing of signals is found in a matrix of interconnected signal paths such as a Butler matrix employed in converting a signal input at one port of the matrix to a set of signals outputted by the matrix for forming a beam. The crossings of signals in such matrix structures have been accomplished, heretofore, by bending one transmission line about another.
A problem arises in that the complexity and size of a microwave structure is increased by signal crossovers employing a bending of one coaxial transmission line about another. It is recognized that a simplified form of such a structure is attained by placing all components and connecting transmission lines in a single plane. However, a multiplicity of crossovers comprising bent transmission lines can produce a considerable amount of stacking of the transmission lines, one above the other. Such a mechanical configuration is both bulky and heavy. Excessive bulk and weight are characteristics which are to be avoided in the construction of antenna arrays, such as those employed in satellites, wherein a reduction in space and weight is most desirable.